A solenoid valve is a valve that generates a magnetic force by applying electric power to its solenoid coil, and controls the flow of a gasoline vapor or air flowing in a fluid passage by driving its valve plunger with the generated magnetic force. A solenoid valve is mounted, e.g., in an engine room, and controls the flow rate of gasoline vapor in a pipe by controlling the power applied to its solenoid coil. The magnetic circuit energized or generated by applying power to the solenoid coil is composed of magnetic members around a coil. In conventional solenoid valves, a bracket for attaching the valve to an outside system is secured to the outer periphery of a yoke by welding.
Thus, in conventional solenoid valves, a bracket and a yoke have been constituted by respective separate members; however, in recent years, to reduce the cost, a technology by which a bracket and a yoke are constituted by the same member has been widespread. Yet, even when a bracket and a yoke are constituted by the same member to be provided for a yoke-bracket, it is necessary to provide a fixed iron core supporting hole in the yoke-bracket in which a fixed iron core is inserted and fixed. The fixed iron core is joined in the supporting hole by welding, spinning, or punching (see, e.g., Patent Document 1). Further, as another fixing method, a technology by which the iron core is fittedly inserted and secured in the supporting hole of the yoke-bracket is also disclosed.    Patent Document 1: JP-A 2004-251315
Since the conventional solenoid valve has been arranged as described above, the following problem may occur: when a fixed iron core is fittedly inserted into and attached to a supporting hole provided in a yoke in order to reduce the cost, not only the weight of the fixed iron core but also that of internal constituent parts such as a coil and the like constituting a magnetic circuit are applied on the supporting hole, and stress caused by the vibration of an engine or the like is concentrated at the supporting hole, which results in deforming, breaking, or wearing out the supporting hole. To deal with such vibration problems, the increase of thickness of a yoke board or the change of material of a yoke board is contemplated; however, other problems may occur: the thickened yoke board makes the working process difficult; and the material-changed yoke board increases the cost.
The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a solenoid valve having high durability to the vibration of an engine or the equivalent without increasing the thickness of its yoke board or without changing the material of its yoke board.